Concentration of gold bearing materials



Patented Nov. 2, 1937 UNITED STATES PATENT oFFncE concnnraarrziz z zow BEARING I 4 Stanley Tucker, London, England, assignor to Minerals Separation North American Corpora- I tlon, New York, N. Y., a corporation of Mary- No Drawing. Application January 24, 1935, Se-

rial No. 3,287. In Great Britain January 30,

- 11 Claims- (Cl. zoo-16s The present invention relates to an improved atives ofcarbonic acid, they of course include process of extracting gold from ores and like alkali xanthatess v materials byaform. of physical concentration de- Various other agents may be present when pending upon the surface properties of the mathe surface-modifying agents are acting upon 6 terial under treatment, such for example as froth the gold particles, as during the above-stated flotation, and has for its general object to propreliminary agitation or grinding operation. vide for simplicity in such extraction, as well The use in this manner of a tin salt, such as as for high gold recovery and high gold assay stannous chloride (SnCli), has been found to of concentrate. reduce the quantity of the mercurial agent which 10 In accordance with the invention, the goldis required. 1 bearing material inthe state of finely-divided As a basis of comparison with the examples particles is formed into apnlp with water both to be hereinafter given, the following test was r in the presence of a mercurial agent and in the carried out:

presence of a sulphidizing agent. By this comcomparative test.

15 bination of agents, as the present inventor has discovered, the gold particles present in the Low-grade gold ore obtainedfrom the Colopulp are so'modifled at their surfaces thatthey mines mine in the Congo was taken. This is a are made amenable to subsequent concentration free gold ore containing a very small amount of dependingupon their surface properties. pyrite and go d in a coarse condition irregularly Instead of the sulphidizing agent, an organic distributed in a hard siliceous gangue. .fi'he ore sulphur derivative of carbonic acid may be emwas crushed until only 2% remained on a:=100 ployed, the combination with such a compound mesh Tyler screen, 2% of charcoalbeing ground of the mercurial agent having also been found with the ore. The ore was then floated with by the present inventor to produce the stated ef- 2 lbs. per ton of stripped blast furnace creosote, feet on the surfaces of the gold fparticles present together with 0.5 lb. per ton of xanthate, pro- 25 in the pulp. However, the claims of this a'ppiiducing a primary concentrate. This concentrate cation should not be construed as covering the was then cleaned by refloating with 0.5 lb. per use of organic sulphur derivatives of carbonic ton of stripped blast furnace creosote and 0.2 lb. acid. which subject-matter is separately claimed per ton of xanthate. By this means a flotation so in an application Serial No. 144,314, filed May 22, test was conducted without the employment of 1987. which is a division of the present applicamercury so as to form a .basis of comparison. tion. It was only found possible to recover 62.3% of In applying the process in apparatus of the the gold by this flotation procedure. The crude kind ordinarily employed for froth flotation and O e as ayed dWtS- 0f 8 p ton and the "w lunction with usual frothing agents so combined concentrates assayed 219 dwts. per that the concentrate floats in,the form of a froth, t of 801i A u Of G could e it has been found that under suitable conditions r oved by p i h flotation i ss wi an almost complete recovery of gold can be obover a corduroy strake. By increasing the grindtained by the process in the form. f a, high ing period from 30 minutes to a total of 60 flhe surface-modifying agents may be i possible to recover 19.1% of the gold in the flopersed among the particles of the gold-bearing tation concentrate, but the assay of the concenmaterial during an agitation or grinding ope trate fell to 49.7 dwts. per ton, the assay of the tion, carried out prior to concentration; crude S p being in this case i 0f .The mercurial agent may be metallic mercury 8 p 45 r a solution of a salt thereof. Mercuric chloride e f owing is a des p n of Certain tests may be used dissolved in an excess of sodium cywhich have been carried .out, from which further anide, a slight excess being sufflcient for the details of the method 0 4 34 O e This solution is believed to de n vention into effect maybeobtained.

the formation of a sodium mercuric cyanide, I c Example I I I a 50 with some free sodium cyanide present. sulpmdjflng agent; hi h hav beentound 500 grammes of the above-mentioned ore asuseful include sulphur, soluble'sulphides or polyseying 11.39 dwts. per ton and crushed at 10 V gulphldea, nd sulphur dissolved in sulphides of mesh were taken and ground with 200 cubic 'polysuiphides. As tothe organic sulphur derivcentimetres of water, 0.125 lb; per ton of mercuric 5 ade concentrate. minutes and forcing the flotation, it was found meshes to the lineal I showed a recovery of 98.8%

of 97.9% of the gold chloride, and 0.075 lb. per ton of sodium cyanide in a pebble mill for 30 minutes, until only about 2% of the material inch. When the grinding had proceeded for 20 minutes, the following agents were added to the mill:

- Pounds per ton Sodium polysulphide 2 Anglo Persian fuel .51 o. 45 Blast furnace creosote 0.078 Pine oil 0.08

The sodium polysulphide was prepared by heatinga solution of commercial sodium sulphide with by weight of flowers of sulphur on the sulphide present.

froth taken for three minutes. concentrates assayed 181.8 dwts.

The combined per ton and of the gold.

Example II was obtained in a concen trate assaying 242.4 dwts. of gold.

In each of the in the comparative test. Similar results were obtained admission to the flotation machine, but it was to employ a somewhat larger quantity of sodium cyanide, up to 0.45

' Example III In this example the same ore was employed as before, but 0.8 of a lb. of mercury per ton of ore was added in the metallic state to the grinding mill in place of the addition of mercuric chloride and sodium cyanide. The ore was ground to 80 mesh, was sulphiclized with sodium sulphide as before, and floated by the aid ofethe following agents:

Pound per ton Anglo Persian fuel oil 0.45 Blast furnace creosote 0.078 Pine oil 0.,08 xanthate 0.5

The first three reagents were added in the grinding mill, and the, xanthate to two equal portions to the flotation machine. sulphide in the amount of 2 lbs. per ton was added to the grinding mill along with the flotation oils.

dwt. per ton, giving a recovery of gold in the concentrate. I

.polysulphide (12.5%

. and as a result 96% of the gold in tained in a concentrate which assayed 190.4 dwts.

, the sample of ore 'yto the mill at the beginning or the grinding stage. The crude ore assayed 11.16 dwts. per ton, sodium flowers of sulphur) was the sulphidizing agent employed, the quantity of this agent was 1.0 lb. per ton, and the ore was ground to pass a 100 mesh screen, the other conditions being the same as in Example III. The recovery of gold was 98.5% and the concentrate assayed 343.6 dwts. per ton.

Broadly similar results with a somewhat lower grade of concentrates have been obtained on Rand Banket ores, and even in the case of an ore assaying only 1.84 dwts. per ton, of 97.7% of the gold has been obtained with the concentrate containing 37.4 dwtsfper ton of gold. All 01 the concentrates mentioned could, by retreatment in bulk, be reconcentrated to a much higher grade.

Emmple V 500 grammes oi ore obtained from Klerksdorp, South Africa, were taken for the purpose of this example. This ore is partly oxidized gold ore containing iron sulphide, and assayed 17.45 dwts.

Der short ton of 2000 lbs. It was ground to passwere therefore ground with the ore for ten minutes.

The resulting material was about such as would pass a screen having 100 meshes to the lineal inch. It was subjected to froth flotation with two additions of 0.25 lb. per ton of potassium xanthate,

the ore was ob- Ezample VI In another test the same ore from Klerksdorp was taken and the same conditions observed, but the sodium polysulphide and olelc acid were omitted, and in their place 2 lbs. per ton of potassium xanthate was added in the grinding mill, the other reagents remaining as before. In this case assayed 12.29 dwts. per ton, and a recovery of 97.7% of the gold was made in a concentrate assaying 177.2 dwts. per ton.

It will be observed that the addition of the xanthate along with the mercury so that the particles become modified by the xanthate during the action of the mercury upon them is the distingulshlng feature quent use of xanthate merely in the flotation operation not being equivalent.

Example VII 500 grammes of crude ore containing 8.68 dwts.

of this grinding, there were of this example. the subserecovery of 97.8% of the gold present. The other agents employed were: r Pound per ton Anglo Persian fuel oil 0.45 Blast furnace creosote .0.0'18 Pine oil 0.08 xanthate 0.8

In another case where the ore contained 17.52 dwts. per ton of gold, under conditions parallel to the g example the recovery was 98.2%

of the gold and the concentrate assayed $34.4 dwts.

of gold per tpn. In this instance the ore was only ground to pass a screen having 80 meshes to the lineal inch, andthe mercury, oils, and

sulphidizing agent were all added to the mill at the beginning of ,the grinding stage, while in the g example the mercury was added alone in the first instance and the other reagents only after minutes grinding.

Example VIII show the career of chloride along with This example is intended to using a proportion of stannous mercuric chloride'with the object of reducing oforewereground of pine oil, 0.078 lb. per

minutes. grinding 2 lbs., per

' taining 500 grammes separated by this method.

ing 120 meshes l p n the quantity of 'mercuryrequired. 500 grammes in 250 cubic centimetres of water for 30 minutes in the presence of 0.05 lb. per ton of Anglo Persian fuel oil, 0.08 'lb. per ton ton of blast furnace creosote, and 3.5 cubic centimetres of a 5% solution of HgCls to which had been added 0.3 cubic centimetre of a solution of SnClr, the latter mixture being gently warmed prior to its addition to the pulp so as to precipitate the mercury. After ton of polysulphide were-added, and grinding was continued for 10 minutes, until'the orepassed a screen hav- I p to the lineal inch.

:Ihe pulp was then floated with the aid of 0.75 lb. per ton of potassium xanthate. The crude ore assayed 22 dwts. per ton of gold, the concentrate assayed 244 dwts. per ton, and a recovery of 08.2% of the gold waseffected.

Example IX The following example shows the effect of working up the mercury into an emulsion with fuel oil prior to its addition to the pulp. 0.8 lb. per ton of mercury wasfworlied up with 0.45 lb. per ton of Anglo Persian fuel oil and added to a pulp conof 10 mesh ore. The whole was ground with blast furnace creosote and pipe oil in the same proportions as in the preceding with 2 lbs. per ton of polysulphide until the ore would, in the main, pass a screen having 150 meshes to'the lineal inch. Flotation with xanthate as before showed a recovery of 98.4%. of gold in a concentrate assaying 137.8 dwts. per ton, the crudevore assaying 2'1 dwts. per

ton.

Example X The following example is of an which concentration was flotation, but by a film heat that a useful recovery can be ore is treated with mercury instance in method, and shows obtained when'the and subsequently by the employ ticles in thepulp are effected not by froth tion.

r finely-divided 500 grammes of a gold a screen having 10 meshes .were ground with 225 cubic. centimetres of water to pass a screen having meshes to the lineal 113311, the following agents being added to the Pounds per ton Mercury 0.8 Flowers of sulphur 0.8 Anglo Persian fuel 0fl & 5.5

After grinding the pulp was carefully deslimed, and the deslimedportion was passed three times over the spitzkastl The gold particles were removed as a film at the overfiow, while the residue was caught at the spigot of the spitzkast. The results on the material fed to the spitzkast were as followswt Au (ms. 1:3

511011 ton fi Feed am a. 51 Film float i4 220. 8 75. 8 Spigot product 3w 8. 2 Mi 2 I claim:-.--

1. A process for the concentration of a gol bearing material consisting in forming a p p of flnely-dividedparticles of the gold-bearing ,in thepresence of a mercurialagent and sulphidizing agent, so that the gold particles in the pulp are modified by said agents and said gold particles made amenable to concentration depending upon their surface properties, and concentrating said gold particles from the material by flotation.

2. A process for the concentration of a goldbearing material consisting in forming a pulp of flneiy-divided-particles of the gold-bearing material with water in the presence of a mersulphidizing agent, so that the surfaces of the gold particles in the pulp are modified by said agents and said gold particles made amenable to concentration depending upon their surface properties, and concencurial agent and a trating said gold particles from the material by 'froth flotation.

3. A process for the concentration of a goldbearing material consisting in the preliminary step of agitating a pulp with water oi' finelydivided particles of the gold-bearing material in the presence of a mercurial agent and a sulphidizing agent, so that the surfaces of the gold particles in the pulp are modified by said agents and said gold particles made amenable to concentration depending upon gold particles from the material by flotation.

4. A process for the concentration of a goldbearing material consisting in the preliminary step of grinding the gold-bearing material with water into a pulp of fine -divided particles in the presence of a mercurial agent and a sulphidizing agent, so that the surfaces of the gold parmodlfied by said agents and said goldparticles made amenable to concentration depending upon their surface properties, and the subsequent step of concentrating said gold particles from the material by flota- 5. A process for hearing material their surface properties, and the subsequent step of concentrating said amenable to concentration depending upon their surface properties, and concentrating said gold particles from the material by flotation.

9. A process for the concentration of a goldcentration depending upon their surface properties, and concentrating said gold particles from the material by flotation.

6. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divided 10. A process for the concentration of a gold- 7 bearing material depending upon their surface properties, and concentrating said gold par-' ticles from the material by flotation.

7. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divlded particles ofthe gold-bearing material with water in and concentrating said gold particles from the material by flotation.

11. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divided particles of the gold-bearing masodium cya id and O B E- S 801d agent and a sulphidizlng agent, so that the surparticles from the material by flotation.

8. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divided particles of the gold-bearing matrial' with water in the presence of a mercurial agent and sulphur, so that the surfaces 01' the gold particles in the pulp are modified by said mercurial agent and sulphur and said gold particles made nable to concentration depending upon their surface properties, said pulp being also formed in the presence 01 stannous chloride, and concentrating said gold particles from the material by flotation.

- STANLEY TUCKER.

CERTI ICATE OF CORRECTION. v

I November 2, 1957. STANLEI, TUCKER.

Patent No. 2,097, 608.

1 of the above numbered patent requiring correction as follows column, line 51+, for the word "of" read or; 52- 55, for asseyiiig" the word "to" Page 1, first same page, second column, lines read saying; page 2, first colum n, line 68, for

case in the Patent Office. I Signed and sealed this 1 t day of February, A. D. 1958.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

- amenable to concentration depending upon their surface properties, and concentrating said gold particles from the material by flotation.

9. A process for the concentration of a goldcentration depending upon their surface properties, and concentrating said gold particles from the material by flotation.

6. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divided 10. A process for the concentration of a gold- 7 bearing material depending upon their surface properties, and concentrating said gold par-' ticles from the material by flotation.

7. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divlded particles ofthe gold-bearing material with water in and concentrating said gold particles from the material by flotation.

11. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divided particles of the gold-bearing masodium cya id and O B E- S 801d agent and a sulphidizlng agent, so that the surparticles from the material by flotation.

8. A process for the concentration of a goldbearing material consisting in forming a pulp of finely-divided particles of the gold-bearing matrial' with water in the presence of a mercurial agent and sulphur, so that the surfaces 01' the gold particles in the pulp are modified by said mercurial agent and sulphur and said gold particles made nable to concentration depending upon their surface properties, said pulp being also formed in the presence 01 stannous chloride, and concentrating said gold particles from the material by flotation.

- STANLEY TUCKER.

CERTI ICATE OF CORRECTION. v

I November 2, 1957. STANLEI, TUCKER.

Patent No. 2,097, 608.

1 of the above numbered patent requiring correction as follows column, line 51+, for the word "of" read or; 52- 55, for asseyiiig" the word "to" Page 1, first same page, second column, lines read saying; page 2, first colum n, line 68, for

case in the Patent Office. I Signed and sealed this 1 t day of February, A. D. 1958.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

